1. Division of Neurology, Department of Medicine, St Michael's Hospital, University of Toronto, Toronto, Ontario, Canada
2. Division of Neurology, Tel Aviv Sourasky Medical Center, Tel-Aviv University, Tel-Aviv, Israel
3. Department of Clinical Neurological Sciences, London Health Sciences Centre, Western University, London, Ontario, Canada
4. Division of Neuroradiology, Department of Medical Imaging, St. Michael's Hospital, University of Toronto, London, Ontario, Canada
5. Department of Neurology, Johns Hopkins University, Baltimore, Maryland, USA